Gerris Ch 20

Ovarian hyperstimulation syndrome (OHSS) is the price patients pay for our attempt to override nature’s delicate balances that were created to assure a single oocyte ovulation. Spontaneous OHSS does occur, as we delineate later. It is, however, very rare. Indeed, natural-cycle-based assisted reproductive technologies (ART) were responsible for the birth of the first IVF baby; however, this method was abandoned because it is cumbersome and, more important, yields poor results in terms of pregnancy rate. Therefore, human menopausal gonadotropin (hMG) has been used for decades in ovulation induction cycles, particularly in the context of in vitro fertilization (IVF). In recent years, recombinant follicle stimulating hormone (FSH) preparations have replaced hMG in most centers. Typically, in these cycles, human chorionic gonadotropin (hCG) is used as a surrogate to luteinizing hormone (LH) for the purpose of oocyte maturation and induction and ovulation. Given its significantly longer half-life (> 24 h versus 60 min for LH1,2), hCG administration results in a prolonged luteotrophic effect, characterized by the development of multiple corpora lutea and supraphysiological levels of estradiol (E2) and progesterone (P). This sustained luteotrophic effect may result in the development of OHSS, still the most frequent and severe complication of ovarian stimulation treatments as described in other chapters of this volume. Although hCG (recombinant or urinary-derived in different doses) is used routinely, other modes of ovulation trigger are also available, namely, recombinant LH, native gonadotropin-releasing hormone (GnRH) and GnRH agonists. The aim of this chapter is to explore the association between the mode of trigger and the risk of OHSS. This association culminates in an OHSS risk-free clinical protocol that is available at the end of the chapter.